Rapid multi-slice MR perfusion imaging with large dynamic range

Abstract

The present invention includes a method and apparatus to perform rapid multi-slice MR imaging without ECG gating or requiring breath-holding that is capable of renal profusion analysis and angiographic screening. An ungated interleaved pulse sequence is applied in rapid succession, followed by a delay interval. The ungated interleaved pulse sequence is repeatedly played out with the predefined delay interval between each application of the pulse sequence. The resulting images provide not only a series of temporal phases of contrast-enhanced blood uptake for renal profusion analysis, but also provide enough dynamic range to include angiographic screening of the renal arteries.

1. A method of acquiring MR images comprising:
 (A) applying an ungated pulse sequence and acquiring multi-slice MR data in rapid succession of a first selected anatomy; 
 (B) providing a delay interval of sufficient length to allow for subject free-breathing, wherein the delay interval is user-prescribed and is in the range of 10-20 seconds to allow for the subject free-breathing; 
 (C) repeating steps (A) and (B) a prescribed number of times; 
 (D) transmitting a notched RF saturation pulse having a stop-band between a pair of pass-bands; and 
 (E) acquiring MR data for the slice location in the stop-band of the notched RF saturation pulse. 
 
     
     
       2. The method of  claim 1  further comprising acquiring MR data of a second selected anatomy simultaneously with the first selected anatomy. 
     
     
       3. The method of  claim 2  wherein the second selected anatomy is a cardiac region of the patient to acquire angiographic information about the patient. 
     
     
       4. The method of  claim 1  further comprising the step of injecting a contrast agent in a patient for perfusion analysis imaging. 
     
     
       5. The method of  claim 4  wherein the first selected anatomy are kidneys of the patient and further comprising reconstructing the MR data acquired into a series of images depicting temporal phases of contrast-enhanced blood uptake for renal function and perfusion evaluation. 
     
     
       6. The method of  claim 1  further comprising reconstructing ungated multi-shot echo-planar images and acquiring the MR data during free-breathing. 
     
     
       7. The method of  claim 1  further comprising applying an interleaved saturation recovery sequence for magnetization preparation before each pulse sequence is played out. 
     
     
       8. The method of  claim 1  wherein the notched RF saturation pulse is designed to saturate all slice locations in a volume of slice locations selected except a slice location in which MR data is to be acquired after the transmission of the notched RF saturation pulse. 
     
     
       9. The method of  claim 1  wherein a width of the stop-band of the notched RF saturation pulse is greater than that of a slice location thickness. 
     
     
       10. The method of  claim 9  wherein a width of the notched RF saturation pulse is a user-selectable parameter. 
     
     
       11. A computerized system configured to play out a pulse sequence for perfusion imaging of an anatomy of interest, the computerized system comprising a computer programmed to apply:
 an interleaved preparation/acquisition sequence having a number of preparation pulses and a number of acquisition slices, wherein each preparation pulse corresponds to a given acquisition slice and is timed to occur such that at least one other preparation pulse and one other acquisition slice occur therebetween; 
 a dead space to provide a delay time sufficient to allow patient free-breathing; 
 a repetition time defining a time of the interleaved preparation/acquisition sequence followed by the dead space; and 
 a scanning session defining a prescribed number of times the pulse sequence with the repetition time is repeated; and 
 wherein the computerized system plays out the pulse sequence to acquire at least 12 contiguous slices within approximately three seconds to accomplish a thorough renal perfusion examination in under 5 minutes. 
 
     
     
       12. The computerized system of  claim 11  wherein the pulse sequence is further defined by a steady state preparation sequence occurring after each interleaved preparation/acquisition sequence and before a next interleaved preparation/acquisition sequence. 
     
     
       13. The computerized system of  claim 11  wherein the pulse sequence is further defined to be played out without an ECG trigger and acquires a series of multiple high-resolution images in rapid succession. 
     
     
       14. The computerized system of  claim 13  wherein the anatomy of interest includes at least both kidneys of a patient in a single slice plane and the series of images acquired depict a series of temporal phases of contrast-enhanced blood uptake. 
     
     
       15. The computerized system of  claim 14  wherein the anatomy of interest also includes angiographic images for combined renal evaluation and MR angiography analysis. 
     
     
       16. The computerized system of  claim 11  wherein the dead space is a user prescribed delay interval to allow magnetization equilibrium. 
     
     
       17. The computerized system of  claim 11  wherein the pulse sequence is further defined by a notched RF excitation pulse having a stop-band between a pair of pass-bands. 
     
     
       18. The computerized system of  claim 17  wherein a width of the stop-band of the notched RF saturation pulse is greater than that of a slice location thickness. 
     
     
       19. An MRI apparatus to acquire multiple MR images having high temporal resolution and increased spatial resolution comprising:
 a magnetic resonance imaging (MRI) system having a plurality of gradient coils positioned about a bore of a magnet to impress a polarizing magnetic field and an RF transceiver system and an RF switch controlled by a pulse module to transmit RF signals to an RF coil assembly to acquire MR images; and 
 a computer programmed to: 
 apply a pulse sequence that interleaves a given preparation pulse and acquisition slice combination with a preparation pulse and acquisition slice for different preparation pulse and acquisition slice combinations, in rapid successions a given number of times, followed by a user-prescribed delay time before repeating the pulse sequence;
 reconstruct a series of multiple high resolution images; and 
 acquire at least 12 contiguous slices within approximately three seconds to accomplish a thorough renal perfusion examination in under 5 minutes. 
 
 
     
     
       20. The MRI apparatus of  claim 19  wherein the computer is also programmed to apply a steady state preparation sequence after the delay time and before a next application of the pulse sequence. 
     
     
       21. The MRI apparatus of  claim 19  wherein the computer is also programmed to apply the pulse sequence with no dead time between slice acquisitions in each interleaved preparation pulse/acquisition slice sequence. 
     
     
       22. The MRI apparatus of  claim 19  wherein the computer is also programmed to acquire images with enough spatial resolution to include both renal perfusion functional images and angiographic perfusion images in one MR image. 
     
     
       23. The MRI apparatus of  claim 19  wherein the computer is further programmed to:
 transmit a notched RF saturation pulse within a selected volume of slice locations, the notched RF saturation pulse having a stop-band between a pair of pass-bands; and 
 acquire MR data in the stop-band of the notched RF saturation pulse. 
 
     
     
       24. A method of analyzing renal function with functional MR imaging comprising:
 (A) injecting a contrast agent in a patient; 
 (B) defining an area of interest to include both kidneys of the patient; 
 (C) applying an interleaved acquisition pulse sequence to the area of interest; 
 (D) acquiring a series of high-resolution images of the area of interest in rapid succession, wherein the rapid succession of image acquisition includes acquiring at least twelve contiguous slices at a rate of approximately 250 msec. per slice such that each series of high-resolution images are acquired in approximately three seconds; 
 (E) allowing a delayed relaxation times; 
 (F) repeating steps (C)-(E) a prescribed number of time; and 
 (G) evaluating the series of images depicting temporal phases of contrast-enhanced blood uptake of both kidneys. 
 
     
     
       25. The method of  claim 24  further comprising reconstructing images having angiographic information as well as renal perfusion data. 
     
     
       26. The method of  claim 24  wherein image acquisition is not timed to any particular cycle of cardiac motion. 
     
     
       27. The method of  claim 24  wherein the delayed relaxation time is user-prescribed. 
     
     
       28. The method of  claim 27  wherein the delayed relaxation time is in the range of 10-20 seconds to allow free breathing by the patient during the delayed relaxation time. 
     
     
       29. The method of  claim 24  further comprising applying a steady-state preparation sequence after the delayed relaxation time to ensure adequate saturation on a subsequent acquisition. 
     
     
       30. The method of  claim 24  further comprising reconstructing a plurality of the series of high-resolution images depicting complete coverage of both kidneys for renal perfusion analysis. 
     
     
       31. The method of  claim 24  applied to a patient regardless of whether breath-holding is demanded.